N-fluorinated substituted aziridines



United States Patent N-FLUORINATED SUBSTITUTED AZIRIDINES Carl C.Thurman, Jr., Lake Jackson, Tex., assignor to The Dow Chemical Company,Midland, Mich., a corporation of Delaware No Drawing. Filed May 11,1962, Ser. No. 194,187

Int. Cl. C07d 23/06 U.S. Cl. 260-239 6 Claims This invention isconcerned with new chemical compounds, a process for making them, andnew polymeric compositions obtainable therefrom. More specifically, itrelates to a new class of substituted aziridines produced by thereaction of 11,5 lower alkylene imines with polyfluorinated olefiniccompounds and to polymers thereof.

It is known that a,,6 alkylene imines such as ethylenimine andpropylenimine which have an unsubstituted nitrogen atom will react byadding at the nitrogen atom to an activated olefinic double bond incompounds such as butadiene, styrene, and alkyl acrylates andcrotonates, thereby forming the corresponding N-substituted aziridines.Although the reaction will sometimes take placewhen the reactants aremerely contacted at ordinary temperatures, it is often necessary toapply heat or employ a catalyst such as an alkali metal, a metal amide,or a metal alcoholate.

It has now been found that the presumably relatively inactive doublebond in certain polyfluorinated olefinic compounds will react in asimilar manner with 11,13 alkylene imines and it has been found furtherthat this reaction proceeds smoothly in the absence of a catalyst and ator only slightly above normal room temperature. The polyfluorinatedolefinic compounds found to be reactive as stated have the structurewherein each X is independently selected from the group consisting offluorine and perfluorinated lower alkyl radicals containing from one toabout four carbon atoms and Y is selected from the group consisting ofhydrogen, halogen, cyano and perfluorinated lower alkyl radicals of 1-4carbon atoms. The alkylene imines with which these compounds react arerepresented by the structure wherein R and R are hydrogen or methyl andR" is hydrogen or lower alkyl of 1-4 carbon atoms. The imines therebyrepresented include ethylenimine, propylenimine, 1,2 butylenimine, 2,3butylenimine, 2,2 dimethylethylenimine, and similar compounds.

The reaction product is an aziridine having a fluorinated alkyl radicalattached to the nitrogen atom. A molecule of hydrogen fluoride may splitfrom the alkyl radical in the course of the reaction and thecorresponding fluorinated alkenyl aziridine is thereby formed. Thetendency to split out HP from the molecule increases with the size andcomplexity of the alkyl group and in many cases, an appreciable amountof splitting occurs spontaneously, yielding a reaction product which isat least in part the alkenyl compound. The product may, therefore, berepresented by the general formula and the symbols X, Y, R, R, and R"represent groups as defined above.

The polyfluorinated olefins described above may be prepared by a numberof methods known to be useful in this general field of chemistry.Suitable means include the pyrolysis of fluorinated lower aliphatichydrocarbons, the reaction of carbon with fluorinated hydrocarbons underappropriate conditions, and the reaction of fluorinated hydrocarbonswith other halogenated hydrocarbons or other fluorides at hightemperatures. For example, trifluoroacrylonitrile can be made by amethod described in US. 2,730,543 wherein a perfluoroolefin is reactedwith an alcohol to make an ether which is converted by hydrolysis of thealpha-fluorine atoms to the corresponding ester, and the ester istransformed into the nitrile by the conventional route through the amideand the saturated nitrile. The preparation of perfluoro-Z-methyl-Z-pentene is described by Dresdner et al., I. Am. Chem. Soc. 82,5833 (1960), the reaction involving contacting perfluoropropylene withnitrogen fluoride in the presence of cesium fluoride at elevatedtemperatures.

The imine-polyfluorinated olefin reaction proceeds smoothly when thereactants are contacted in the liquid state at temperatures from about-70 C. to about 60 C. under atmospheric or superatmospheric pressure.Normally, and preferably, the reaction is carried out at a temperatureof 0-45 C. under atmospheric pressure or the autogenous pressure of thesystem. While most of the polyfluorinated olefins described will reactat room temperature or below, it is necessary to warm the reactionmixture to about 40 C. when tetrafiuor'oethylene is being reacted. Underthe reaction conditions described, vinyl fluoride and vinylidenefluoride do not react with alkylene imines.

At least about one mole of olefin per mole of imine is used in thepreparation of these compounds Preferably, from 1.05 to about 2.0 molesof olefin are employed per mole of imine for best results.

Inert organic solvents such as hexane, benzene, cyclohexane, fluorinatedsaturated hydrocarbons, and diethyl ether may be used in the reactionmixture, but their presence is usually not desirable.

The separation of the product from the reaction mixture is usuallyaccomplished by venting or vaporizing off any excess flourinated olefinand filtering or decanting to remove any solid polymer which may beformed. The product may then be separated and purified if desired bydistillation, extraction, or by chromatographic methods. Because of thetendency of these new compounds to polymerize or to lose a molecule ofHF, thereby forming a fluorinated alkenyl aziridine, any distillation ispreferably done at as low temperature and in as short a time aspossible. The unsaturated compounds formed by the splitting out of HP insome of these preparations, although having properties similar to thoseof the corresponding saturated compounds, are nevertheless separablefrom them by the methods mentioned. Vapor phase chromatographicseparation is often an advantageous procedure.

The purified compounds are clear colorless liquids with a characteristicammoniacal odor. The preparation and the properties of representativecompounds are described in the following examples.

Example 1 A stainless steel pressure reactor equipped with a pressuregauge and pressure relief means was evacuated and cooled to liquidnitrogen temperature. To the evacuated reactor there was added insequence 193 g. of perfluoropropylene (C F and 48 g. of ethylenimine.The reactor was then allowed to warm to room temperature while beingrotated to agitate the reaction mixture. After two hours, the reactorwas opened and 8.9 g. unreacted propylene was vented off and collected.The reaction product consisted of 16.5 g. of polymeric solid and 210 g.of a yellowish liquid of ammoniacal odor. This liquid was analyzed byinfrared spectroscopy and by mass spectrophotometry and was found to bea mixture of 84.6 percent by weight of1-(1,1,2,3,3,3-hexafiuoropropyl)aziridine and 15.4 percent of 1-(l,2,3,3,3 pentafluoro-lpropenyl)-aziridine. A sample of1-(1,1,2,3,3,3-hexafluoropropyl)aziridine purified by vapor phasechromatography was a colorless liquid having a boiling point of 93.9" C.and a refractive index, n :1.3215. The unsaturated compound was also aliquid having similar properties.

Example 2 In a reactor similar to but smaller than that used in Example1, 42.3 g. of bromotrifiuoroethylene and 8.2 g. of ethylenimine werecombined under the previously described conditions. After two hours,10.5 g. of unreacted bromotrifiuoroethylene was removed from thereactor, leaving 36.0 g. of liquid which was found to be better than 90mole percent of 1-(2-bromo1,1,2-trifluoroethy1)aziridine. A purifiedsample of this compound was a clear, yellowish liquid of ammoniacal odorand having a boiling point of 133 C., refractive index 12 1.4118.

Example 3 As shown in Example 2, 23.5 g. of chlorotrifluoroethylene and5.55 g. of ethylenimine were combined and allowed to react for two hourswhile the reactor was warming to room temperature. Excess, unreactedchlorotrifluoroethylene amounting to 4.9 g. was then removed from thereactor and collected. The product of reaction was a liquid, 14.5 g. inquantity, proving upon analysis to be 9095 mole percent1-(2-chloro-1,1,2-trifluoroethyl)aziridine. A purified sample had aboiling point 112 C., refractive index n 1.3825.

Example 4 As shown in the above examples, 24 g. of tetrafiuoroethyleneand 5.88 g. of ethylenimine were combined and allowed to warm to roomtemperature. The reaction mixture was then heated further to about 45 C.After a reaction time of 3 hours, the reactor was opened and 2.8 g. ofunreacted tetrafluoroethylene was recovered. The liquid reaction productamount to 12.5 grams and was found by analysis to be 9095 mole percent1-(1,1,2,2- tetrafiuoroethyl)aziridine. A purified sample had B.P. 80C., n 1.3324.

Example 5 By the procedure described in Examples 1-3, 13.8 g. ofperfluoro-2-methyl-2-pentene and 1.6 g. of ethylenimine were mixed andallowed to react. Essentially all of the ethylenimine reacted and aclear liquid of ammoniacal odor was formed which was found to consistlargely of 1 (2,3,3,4,4,4 hexafluoro 1,1 bis(trifluoromethyl)-butyl)aziridine with a minor proportion of 1-(2,3,4,4,4- pentafluoro1,1-bis(trifluoromethyl )-2-butenyl aziridine. These compounds, whichhave closely similar properties, are separable as described above.

4 Example 6 Example 7 As in Example 6, 4 ml. of trifluoroacrylonitrileand 0.5 ml. of ethylenimine were combined and allowed to react tocompletion. The product was a clear liquid of characteristic odor. Itwas found by infrared and mass spectroscopic analysis ot consistessentially of 1-(2-cyano- 1,1,2-trifiuoroethyl) aziridine.

Example 8 Excess perfiuoropropylene was mixed with propylenimine in theliquid state and allowed to react, the mixture warming rapidly to aboutroom temperature in the process. Removal of the excessperfluoropropylene left a residue of a clear ammoniacal liquid which wasfound by spectroscopic analysis as before to consist largely of 1-(1,1,2,3,3,3-hexafluoropropyl)-2-methylaziridine with some 1-(1,2,3,3,3-pentafiuoro-1-propenyl) -2-methylaziridine.

In a similar manner, perfiuoropropylene and other fluorinatedolefinically unsaturated compounds as shown in the foregoing examplesreact with other u,[i-alkylene imines such as 1,2-butylenimine,2,3-butylenimine, and 2,2-dimethylaziridine to produce the correspondingN- substituted aziridines. For example, when combined as shown above,tetrafluoroethylene and 1,2-butylenimine react to form2-ethyl-1-(1,1,2,2-tetrafiuoroethyl)-aziridine, bromotrifiuoroethyleneand 2,3-butylenimine react to form 1 (2--bromo-1,1,2-trifluoroethyl)2,3-dimethylaziridine, andchlorotrifiuoroethylene reacts with 2,2-dimethylaziridine to form1-(2-chloro-1,1,2-trifiuoroethyl)- 2,2-dimethylaziridine, all asprincipal products of the reaction. Similarly, compounds such as 1-(1,1,2-trifiuoroethyl) 2-methylaziridine,1-(2-cyano-1,1,2-trifiuoroethyl)-2-methy1aziridine,

1-( 1,1,2,3,3,3-hexafiuoropropyl)-2-methylaziridine and1-(2-chloro-1,1,2-trifiuoroethyl)-2-methylaziridine are easily made.

These compounds are useful as additives to textile fibers, paper, andpaper products to improve their physical properties. For example, thedry strength of Whatman No. 1 filter paper was greatly increased bywetting a sample with 1-(1,1,2,3,3,3-hexafluoropropyl)-aziridine andallowing it to air-dry. Comparative strength tests are shown in Table I.

TABLE I Ultimate Burst Tensile Strength, Strength. Test Strip lbs/sq.in. 1bs./sq. in,

Untreated 7 1, 280 Treated 38 3, 325

aziridine were each polymerized by the addition of a small quantity ofHCl at room temperature. An exothermic polymerization occurred which wascontrolled by moderate cooling, yielding in each case a clear viscousliquid polymer. These liquids formed clear adherent films when appliedto glass or metal and allowed to dry. The films were water sensitive butnot water-soluble.

By more strenuous conditions, polymers of increased strength andchemical resistance are obtained. When the fluorinated substitutedaziridines described in this specification are heated at refluxtemperature over a period of hours, tenaciously adherent polymeric filmsare formed on the inner surfaces of the flask and reflux column. Thesefilms are not affected by boiling organic solvents and resist evenchromic acid cleaning solution. This procedure, may, therefore, be usedto cover glass, metal, or other surfaces with a tough adherent inertcoating.

I claim:

1. A compound of the formula wherein R and R are selected from the groupconsisting of hydrogen and methyl, R is selected from the groupconsisting of hydrogen and alkyl radicals containwherein each X isselected from the group consisting of fluorine and perfluorinated alkylcontaining from one to four carbon atoms, and Y is selected from thegroup consisting of hydrogen, halogen, cyano, and perfluorinated alkylcontaining from one to four carbon atoms.

2. 1-(2-cyano-1,1,2-trifluoroethyl)aziridine.

3. 1-(1,2,3,3,3-pentafluoro-l-propenyl)aziridine.

4. 1-(1,2-difluorovinyl)aziridine.

5. 1 (2,3,4,4,4 pentafluoro 1,1 bis(trifluoromethyl -2-butenylaziridine.

6. 1-(l,2,3,3,3-pentafluoro 1 propenyl)-2-methylaziridine.

References Cited UNITED STATES PATENTS 3,057,864 10/ 1962 Shulgin.

OTHER REFERENCES Brace: Journal of Organic Chemistry, vol. 26, N0. 10,October 1961, p. 4008.

ALTON D. ROLLINS, Primary Examiner U.S. Cl. X.R.

1. A COMPOUND OF THE FORMULA 